A used Audiolab 8000C would fit the bill. I used one for a while and found it excellent. It is right in the middle of your price range.
Another option would be to sell the ATI and get an integrated amp (like an excellent Cyrus 2) since you will not need anywhere near that much power for the green mountains (I own the Europas), and an integrated amp will likely give you better overall quality in the price range you're looking at.
Another option would be to sell the ATI and get an integrated amp (like an excellent Cyrus 2) since you will not need anywhere near that much power for the green mountains (I own the Europas), and an integrated amp will likely give you better overall quality in the price range you're looking at.